That is the grant for the EPA software, not the network of embassies for adding embassy data to the EPA program.

I'm not sure what maintenance you mean there, but it surely is reminiscent of "I could code Twitter in a weekend."

Yes, but the same contractor manages the AirNow Data Management Center [0], and according to this talk [0] DOSAir is the actual program here, and they are piggybacking the EPA AirNow data infrastructure, and per the OP they are keeping the sensors running.

So I'm all the more confused about what exactly necessitates this specific State Dept-directed funding freeze that happens to impact only the network that communicates the data from embassies into AirNow, but not the data center or other data producers.

[0] https://www.airnow.gov/sites/default/files/2020-11/hylton-st...

[1] https://youtu.be/RcdBIWdA-e4?si=PTpOEG7rFnGod7EH&t=2615

The ending of that comparison is that Twitter's strength is that it takes far more effort to build it's network effect. Air quality data is easy.